Research Abstracts Online
January - December 2011

PI: Name Withheld

Accuracy of Computed NMR Chemical Shifts

The focus of this project is to improve the accuracy NMR chemical shifts computed with density functional theory (DFT). Improved accuracy would allow computer modeling to reliably capture the subtle chemical shift differences between diastereomers. It is believed that computed 13C NMR shift errors are due to sub-par orbital energies that are expressed through the paramagnetic portion of the nuclear shielding equation.

These shift errors may be indicative of an inadequate DFT functional. This researcher has previously evaluated a number of DFT functionals in an effort to find the best functional for computing 13C chemical shifts. While successful in identifying the most accurate functionals, it was also clear that in some situations these functionals failed to correlate well with experimental 13C NMR chemical shifts.

Since then, new DFT functionals have been developed. One in particular, the M06 functional, has been shown to be an excellent predictor of organic structure and reaction energetics. This researcher is using MSI resources to evaluate the ability of the M06 functional to accurately compute NMR chemical shifts.